"A New Method for the Carbon-extension Reactions of Azetidin-2-ones", Kobayashi et al., J.C.S. Chem. Comm., 1980, 736-737, describes treatment of 4-sulfonylazetidin-2-ones and 3-triphenylmethyl-4-sulfonylazetidin-2-ones with Grignard reagent. Specifically utilized as starting materials are 4-phenylsulfonylazetidin-2-one and 3-triphenylmethyl-4-methylsulfonylazetidin-2-one.
U.K. Patent Application No. 2,071,650, published Sept. 23, 1981, describes (S)-3-acylamino-2-oxo-1-azetidinesulfonic acids having various substituents in the 4-position, and the use of these compounds as antibacterial agents.
"Transformations of Penicillins. Part V. Reactions of Olefin and Acetylene Derivatives with the Sulphenic Acid Intermediates from Penicillin S-Oxides", Ager et al., J. Chem. Soc., Perkin Trans. I, 1187 (1973), describes the trapping reaction of, inter alia, norbornadiene with the sulphenic acids produced by heating penicillin S-oxides followed by reduction to yield ##STR5##